GLOBAL CHALLENGES

Converting Waste Heat into Electricity

Rebecca Kutzer-Rice | Date: 10-07-10 | Comments

A new device that captures waste heat and converts it into electricity could increase the efficiency of solar panels, car engines and power plants�all while rendering CFCs and complicated turbines obsolete.

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Converting Waste Heat into Electricity
A few weeks ago, I wrote about a new technique by which energy can be harvested from the air. Now scientists at the University of Arizona (UA) are looking to harness power from waste heat with a theoretical device that could reduce fossil fuel use, increase factory efficiencies and make chlorofluorocarbons (CFCs) obsolete.

Current methods of heat conversion, such as refrigeration and steam turbines, require complex mechanics and ozone-depleting chemicals. In the new theoretical model, called a molecular thermoelectric device, a rubberlike polymer is placed between two metals, which serve as electrodes. The material could prove to be an inexpensive and environmentally friendly alternative to traditional heat-conversion devices.

The ringlike structure of the molecules causes electrons to interfere with one another and build up voltage (source: Justin Bergfield, University of Arizona).

"Thermoelectricity makes it possible to cleanly convert heat directly into electrical energy in a device with no moving parts," says Justin Bergfield, a doctoral candidate in the UA College of Optical Sciences. "Our colleagues in the field tell us they are pretty confident that the devices we have designed on the computer can be built with the characteristics that we see in our simulations."

The scientists' work relies on basic laws of quantum physics, particularly wave-particle duality. In this law, tiny particles, such as electrons, can exist as both particles and waves.

"In a sense, an electron is like a red sports car," explains Bergfield. "The sports car is both a car and it's red, just as the electron is both a particle and a wave. The two are properties of the same thing. Electrons are just less obvious to us than sports cars."

The team applied the laws of quantum physics to their work with polyphenyl ethers, molecules that spontaneously amass into polymers. Polyphenyl ether molecules have backbones of benzene rings, which form from carbon atoms. The unique chain-link structure of these molecules allows electrons to easily travel.

"We had both worked with these molecules before and thought about using them for a thermoelectric device," Bergfield says, "but we hadn't really found anything special about them until Michelle Solis, an undergrad who worked on independent study in the lab, discovered that, low and behold, these things had a special feature. As you increase the number of benzene rings in each molecule, you increase the power generated."

Next: Quantum Interference >>